Anyone who has spent time on a frozen lake in winter has heard the eerie sounds of deep groaning and sudden cracks echoing across the ice. While it might sound unsettling, these noises are completely natural. Ice expands and contracts with temperature changes. When the temperature drops suddenly, the ice shrinks and cracks form, creating sharp, gunshot like sounds. When the temperature rises, the ice expands, and deep, moaning vibrations can be heard as the pressure shifts. Despite these sounds, thick ice remains strong.